Ground strap



May 22, 1951 M. D. BERGAN 2,554,169

GROUND STRAP JJM.. nu

INVENTOR. /VAPT//v 0. 5f/P @AW Patented May 22, 1951 GROUND STRAP MartinD. Bergan, Westfield, N. J.,4 assignor to The Thomas & Betts Co.,Elizabeth, N. J., a corporation of New Jersey Application March 30,1946, Serial No. 658,490

6 Claims. (Cl. 173-273) The invention relates in general to a groundstrap for mechanically and electrically connecting a ground wire with aWater pipe or other form of grounded conductor. Such conductors are ofdifferent diameters and it not infrequently happens that an operatordoes not know what size of pipe or conductor he might encounter on anyparticular job where'he desires to make a temporary or permanentgrounding connection. It has been necessary heretofore to provide theoperator With grounding straps of different dimensions and sizes inorder to meet the different requirements relative to size which he mayencounter in making such connections. Accordingly one of the objects ofthe invention is to provide a form of ground strap which is of a lengthto provide a strap of diierent circumferential lengths, which can bereadily bent in situ by the operator to accommodate it to the particularsize of tubular pipe or other form of grounded conductor to which theground wire is to be attached.

While the size of the pipe may vary, the Electric Code at presentpermits the use of only one size of grounding conductor, that is #8 AWGgauge solid Wire of a normal diameter of 0.128 inch for use with acopper strip type of ground strap.

It has been known in the art as shown by the patent to S. N. Buchanan1,922,077, August 15, 1933, to provide a grounding strap in which thegrounding wire is first bent into am, hairpin or loop form and insertedinto the holding element of a clamp organized to get sulcient pressureto prevent the conductor from turning or otherwise moving in the clamp.However, in actual practice it has been found that as a rule theinstalling operator will not go to the trouble of initially bending thegrounding wire into a hairpin loop but insists on leaving the end of thewire unbent and more or less straight and hopes that it Will be heldeven though under these conditions only one side of the conical elementof the clamp engages the wire. However, the wire receiving space in theBuchanan and similar forms of clamps has considerable leeway forpositioning the loop, and which if the wire is straight would notproperly locate the parts to afford a good clamping effect.

Accordingly the primary object of the invention is to provide a form ofground strap which will effectively secure a ground wire thereto underthose conditions wherein the clamped end of the wire is straight.

Broadly this objective is attained first by providing a form ofground'strap, an outturned end portion of which forms the relativelyfixed element of a clamp and which fixed element is designed to engageone side of the straight end ground wire over a material and extensivelength thereof and which fixed element is also backed solidly by thepipe or other rugged support encircled by the strap; and second byproviding as the relatively movable clamping element of the clutch apressure distributing plate or pad for engaging the ground wire on theside thereof opposite the side bearing on the fixed clutch element andengaging the wire over an equally material and extensive length of thestraight end of the wire.

Still another feature of the disclosure is that the device in additionto its Wire clamping features is designed in its outturned end portionforming the fixed clutch element to provide a pair of offset loopscapable of performing two functions: rst, to act as stops to restrainrotation of the pressure distributing plate after contact with the wireand particularly as the plate approaches its final clamping position,and second, the loops provide a pair of aligned tube-like orificesdimensioned just large enough to receive the straight end of a standardsize of grounding wire with a snug but sliding fit and organized tolocate and temporarily secure the wire in proper position in the clampbetween its broad bearing relatively fixed and movable elements evenbefore the clamping pressure is applied.

In the known art the ground strap had to be made sumcently flexible sothat at least one of its clamping portions could be deformed, as bymeans of the conical wedge in the above identilied patent, intoengagement with the U-turn of the grounding Wire, and in turn to forcethe wire loop into binding engagement With the companion and equallydistortable portion of the clamp. There are many situations Where a morerugged and thus less exible type of grounding strap is desired than isnecessary to form the relatively light form of clamp disclosed in theBuchanan patent. However, with increase in cross sectional area of thematerial of which the clamped portion is formed, it becomes more andmore impossible in practice to flex or distort the clamping portions ofsuch known forms of fitting so as to clamp the grounding wire, and thisbecomes more and more diiiicult, and often iinpossible, where aparticularly small size of clamping device is used and where it is notalways possible to bend the ends of the conductor into the U-loop formheretofore used and which had to be bent in order to provide thenecessary holding,

effect.`

Accordingly. another object of the invention is to provide a standardform of ground fitting of a single size which can receive the usualgrounding wires, and which can secure the same directly to the strapwithout necessity of bearing through some portion of the strap and inthis way avoid the necessity of involving any element of flexibility ordistortability of the strap in the clamping operation.

The invention herein disclosed then particularly features a singleclamping means operatively connected to both conductor and wire so thatwhen moved into its tightened position, it will cause the strap first toaccommodate itself to the particular grounded conductor which is tosupport it, then it will firmly clasp itselfv to the supportingconductor and in the nal stages of its clamping movement will secure theground wire fixed securely to the ground strap and the ground strap tothe supportingv conductor all with one tightening operation.

Various other objects and advantages of the invention will be in partobvious from an inspection of the accompanying drawings and in part willbe more fully set forth in the following particular description of oneform of' device embodying the invention, and the invention also consistsin certain new and novel features of construction and combination ofparts hereinafter set forth and claimed.

In the accompanyingl drawings:

Fig. 1 is a plan view of a flat punched blank of thiny sheet metal fromwhich the ground strap herein featured is formed;

Fig. 2 is a view in side elevation of the blank of Fig. 1 with one endpre-formed and showing the strap before it is bent into the finalposition engagingv a water pipe;

Fig. 3 is a slightly enlarged plan view looking down upon the strapformed from the Fig. 2 disclosure bent and locked in operative positionconnecting a water pipe with a ground wire;

Fig. 4 is a view in side elevation of the structure shown in Fig. 3;

Fig. 5 is a transverse sectional view through the pipe, taken on theline 5-5 of Fig. 3 looking in the direction indicated by the arrow andshowing the ground strap in side elevation;

Fig. 6 is a similar view showing the ground strap in section,l taken onthe line 6 6 of Fig. 4 f

and looking in the direction indicated by the arrows; and

Fig. '7 is a detailed plan View of the under side of the clamping nutshown in the preceding gures.

In the drawings there is shown two conductors, a relatively largeconductor A specifically intended to disclose a grounded water pipe, anda cable B provided with a` conductor C hereinafter referred to as aground wire.

The strap I particularly forming the subject matter of this disclosureis designed to connect the conductors A and C both mechanically andelectrically.

The strap comprises one main and three minor parts; a strip of flexiblemetal I I, a bolt I2, a nut I3 threaded on the bolt and a clamping broadfaced bearing saddle or pressure distributing plate I4 loose on the boltand forming a washer or pressure pad or plate tted beneath the headofthe bolt. The strip I I is provided adjacent one. end with a rst bolthole I and in spaced relation thereto with other bolt holes I6 of whichfour are shown in the blank of Fig. 1. The strip II is provided onopposite sides of the bolt hole at right angles thereto.

I5 with a pair of short parallel slits I'I and I8. The material betweenthe slits I'I and I8 is bent inwardly out of the plane of the strip toform a relatively long inner loop I9. The material between each of theslits and the adjacent outer edge of the strip are bent. outwardly toform a pair of outer loops 20 and 2|. It will be noted by reference toFigs. 2 and 5 that the loops 20 and 2l with loop I9 offset therebetweenforms an opening tube or long eye 22 designed to receive the straightend portion of a small diametered conductor C snugly fitted therein asparticularly shown in Figs. 3-6. The slitted end of the strip ispreformed as indicated at the left of Fig. 2 and as hereinafterdescribed and it is this partly formedarticle` which is delivered to theoperator when he leaves the shop to make the connections. rIhemid-portion of the strip as shown in Fig. 2 is bent around therelatively large diametered conductor A to form a clutching band 23which almost completely encircles the conductor and is provided with anupper outstanding portion 244 and an opposing lower outstanding portion25. The portion 2,4 is bent into a step 26, the lower free edge 2 ofwhich finally abuts the portion 25' The bolt I2V is passed' through thebolt hole I5 and whichever one of the bolt holes I6 may happen to bemore or lessr aligned therewith after the band 23 has been formed.

It is a feature of this disclosure that the clamping plate I4 is afreely floating member andV is sufficiently rigid to transmit squeezeforces therethrough without deformation. The plate is located beneaththe head 29, of the bolt and throughl which plate the bolt extendsloosely. It is noted that the clamping plate is non-circular and,specifically, is rectangular in plan and fits between the stops, formedby the outstanding loops 20 and 2I so that this plate does not turn withthe bolt. .The plate I4 overlaps and bears directly on the conductor Cas best shown in Fig. 6 and the parts are so disposed that when the boltis drawn tight the under side of the plate is forced into engagementwith the portion of the conductor C exposed thereto. Preferably, the,under side 36 of the plate I4 is corrugated or otherwise roughened toenhance the engagement between this plate and the conductor.

In operation and assuming that the parts are in the positionapproachingl those shown in Figs. 5 and 6, the tightening of the bolt,will first draw the band 23 tightly into engagement with the conductorA, and this, will continue until edge 2l is bearingl rmly on theprojection 25. At this time the threaded nut I3 will be bearing on theportion of the strap which contains the bolt hole I5 through which theshank end of the bolt is projecting. At the beginning of the bolttight.- ening operation itI will be necessary to hold nut I3 fromrotating with thebolt.

The continued rotation of the bolt will then cause its head 2S to actthrough the clamping plate I4 to cause the` conductor C to bind firmlyagainst the lower loop I9, and at the end of the` tightening movementslthe several parts will be in the position shown in Fig. 6. If theconnection is to` be permanent the surplus length of metal strip beyondthe bolt hole I6, then in use will be cut, olf to provide a neat form ofconnection.

I claim:

1. A groundstrap comprising a, strip of flexible sheetv metal providedadjacent one end with a. rst bolt hole and with a second bolt hole inspaced relation to the'rst hole, said strip adapted to be'bentcircularly into position to encircle a supporting conductor to bring thebolt holes into axial alignment, the portion of the strip on oppositesides of the iirst hole and offset therefrom inwardly frornthe adjacentend of the strip being slitted lengthwise of the strip and with theportion between thevslits ybent inwardly out of the plane of the stripto form an inner loop forming an outwardly exposed relativelyfixedelement of a clutch, and the outer portions between each slit andthe adjacent edge of the strip being both bent outwardly of the plane ofthe strip to form a pair of outer loops disposed oiset from the innerloop, said inwardly bent loop and said pair of outwardly bent loopscoacting to form in eiect a tube adapted to receive a ground wireintruded therein, a single clamping means for mechanically .andelectrically securing the ground wire to the strap and to secure thestrap to the support, said means including a headed bolt passed throughthe aligned bolt holes, a non-circular clamping plate through which thebolt is loosely passed and which constitutes the coacting movableelement of the clutch, said clamping plate located between the head ofthe bolt and the ground wire for directly engaging the ground wire overa material length thereof and to force the same into engagement with thefixed clutch element, said plate being iitted between the outer pair ofloops and held thereby from rotating with the bolt, and a nut engagingthe opposite end of the bolt and adapted to bear on the portion of thestrip provided with the second hole.

2. The ground strap dened in claim 1 and in which the underside of theclamping plate which is designed to engage the ground wire is roughened.

3. The combination with two conductors of materially different diametersand in which a straight end of the smaller conductor extends in closerelation to and parallel to the larger conductor, a strap forming devicefor mechanically and electrically connecting said straight end of thesmaller conductor to the larger conductor, said device including aflexible band substantially encircling the larger conductor and whoseend portions project from the larger conductor to form paralleloutstanding overlapping flanges, one of the flanges provided Vwith threeloops integral with their associated flange having a common axis andcoacting to encircle closely said straight end, the middle loop disposedin bearing engagement with the larger conductor and the two end loopsoffset outwardly from the middle loop to leave the portion of thestraight end between the end loops outwardly exposed, means forsqueezing the flanges towards each other to bind the band on the largerconductor and to bind the straight end on to the middle loop whichoverlaps the same, said means including a headed bolt and nut assemblypassed through the iianges and a pressure plate fitted between the twoouter loops and held thereby from rotating and bearing directly on theportion of the straight end so exposed between the end loops.

4. In a ground strap connector, the combination of a flexible strip ofmetal adapted to be wrapped about a first conductor to form acylindrical portion and provided with overlapping end portionsoutstanding radially from the cylindrical portion, said end portionsprovided with a pair of aligned bolt holes, the upper of the out- 6standing end portions provided with a pair of parallel slits on oppositesides of the bolt hole therein, the portion of metal between each slitand the adjacent edge of the strap being bent upwardly to form a pair ofupper loops and the portion of metal between the slits being bentdownwardly to form a lower loop, said loops being coaxially aligned andforming in effect an incomplete tube fashioned to receive therein and tohold in place a second conductor, a clutch for clamping the secondconductor directly to the lower loop of the strap, the lower loop beingoffset from its associated bolt hole towards the cylindrical portion andforming the relatively fixed jaw element of the clutch, a freelyfloating plate rectangular in plan iitted in the space between the upperloops, otherwise independent thereof and forming the coacting,relatively shiftable jaw element of the clutch, said plate provided witha bolt hole substantially aligned with the said pair of bolt holes, thepart of the plate which lies between its bolt hole and the cylindricalportion of the strap overlapping the iixed jaw element of the clutch fordirect bearing engagement with the second conductor, and pressurecreating means passed through the bolt holes and reacting between theiixed and movable clutch elements to draw them together and thus securethe second conductor to the strip.

5. In a ground strap connector, the combination of a iiexible strip ofmetal adapted to be wrapped about a rst conductor to form a cylindricalportion and provided with overlapping end portions outstanding radiallyfrom the cylindrical portion, said end portions provided with a pair ofaligned bolt holes, the upper of the outstanding end portions providedwith a pair of integral loops upstanding from the portion between theloops, said loops being coaxially aligned to form in effect anincomplete tube fashioned to receive therein a second conductor and saidloops being axially spaced apart to expose therebetween a portion of thesecond conductor, a clutch for clamping the second conductor to thestrip, the part of the upper end portion between the loops forming therelatively iixed jaw element of the clutch and adapted to form a seatfor receiving the portion of the second conductor exposed between loops,a freely floating pressure distributing plate fitted between the loopsand restrained thereby from rotary movement, said plate provided with abolt hole substantially aligned with the said pair of bolt holes, andthe part of the plate which lies between its bolt hole andthecylindrical part of the strap overlapping the ixed jaw element of theclutch, and a headed bolt passed through the pair of aligned bolt holesand through the bolt hole in the floating plate, the head of the boltbearing downwardly on the shiftable clutch element, and a nut on thebolt bearing upwardly on the lower outstanding end portion of the strap.

6. A ground strap sufficiently flexible to be wrapped about acylindrical form of support to form an incomplete circle and with theends of the strap outstanding from said circle and disposed inoverlapping parallel relation to form a pair of overlapping flanges,threaded fastening means including a headed bolt passed through theanges and provided at the end opposite its head with a nut for engagingthe adjacent ange, the portion of the strap between the bolt and thecircle and at the headed end of the bolt provided with a pair ofparallel slots with the ma 57, terial between the slots pressed towardsthe circle to form a concaved L-shaped shoulder forming a relatively xedelement of a clutch and the portions of the material outwardly of eachof the slits pressed outwardly away from the circle to form a pair ofoutstanding loops, said loops and shoulder coacting to receive aconductor therebetween with the outer side of the conductor opposite theshoulder outwardly and upwardly exposed between the loops, and apressure pad rectangular in plan loose on the shank of the bolt,underlapping the head of the bolt, tted between the loops and held fromrotation thereby, said pad forming a Shiftable clutch element with theportion on one side of the bolt and located between the loops, disposedto bear on the exposed outer side of the conductor with a squeeze forcedirected diametrcally through the conductor leaving the opposte portionof the pad .free to assume'what` ever position it may, and said pressurepad being otherwise free of the strap.

MARTIN D. BER'GAN.

REFERENCES -CITED The following references are of record in the file 4ofthis patent:

UNITED STATES PATENTS Number Name Date 931,706 Stevens Aug. 17, 19091,163,372 Schade Dec. 7, 1915 1,495,493 Lipschutz May 27, 1924 1,542,074Mayer June 16, 1925 1,725,120 Williams Aug. 20, 1929 1,809,009 AndreJune 9, 1931 1,922,077 Buchanan Aug. 15, 1933 2,062,690 Weynand Dec. l,1936

